This application claims the priority of German application 197 13 244.8, filed Mar. 29, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a reformation reactor with a reaction chamber through which a gas stream to be reacted is conducted, and into which a charge of a catalyst material is loaded.
Reformation reactors are known in a wide variety of versions, for example for steam reformation of methanol for obtaining hydrogen, which can be used, for example, as fuel for a fuel cell system. Reactors of this kind are disclosed in, e.g., DE 4423587 A1 and DE 4420752 A1.
In many cases, during the operation of such known reactors, as a result of chemical processes, a reduction in the volume of the catalyst charge takes place in the reaction chamber. This reduction results in a reduction of the reaction rate.
U.S. Pat. No. 2,671,719 discloses a reformation system for industrial production of hydrogen and carbon monoxide, in which initially a hydrocarbon with a metal oxide is reacted in a reduction reaction chamber to form oxides of carbon, hydrogen, water, and free metal, and the associated suspension is then fed as a fountain into a reformation reaction chamber. In this reaction chamber, a solid phase is formed, from which solid particles precipitate and consist of free metal or a reformation catalyst, for example nickel or iron, which is carried in the aluminum or magnesium oxide. The iron component acts as an oxygen carrier, while nickel and the aluminum or magnesium oxide function as primary reformation catalysts. By means of a loading funnel and a supply line which extends from the funnel diagonally downward into the reformation reaction chamber, in which line a valve is provided, by suitable operation of the valve, free iron is added to the reformation reaction chamber. Thereby, significant formation of iron oxide is observed there and for this reason, the solids are released from the reaction chamber through an outlet line.
Utility Model DE 90 00 903 U1 describes a reactor for performing catalytic gas reactions having an essentially spherical pressure-resistant reactor jacket and a spherical catalyst bed located in the reactor jacket, a synthesis gas inlet with a synthesis gas distributor located in the center of the spherical catalyst bed, and at least one synthesis gas outlet. To form a synthesis gas flow which is defined radially from the inside to the outside, the synthesis gas distributor is configured spherical with a perforated outer surface. The synthesis gas outlet is formed by a plurality of gas outlets distributed over the reactor jacket with gas collecting lines penetrating the reactor jacket. In the vicinity of the top of the reactor, a catalyst dome is filled with stored catalyst which can slide automatically downward into the reactor jacket to compensate volume when the reactor is initially started.
DE 40 31 514 A1 discloses a tube sheet reactor for performing catalytic processes in which the catalyst material contained in the tubes shrinks by chemical reduction, for example by way of hydrogen and/or carbon monoxide when the reactor is started, by a certain volume. The upper free ends of the catalyst tubes are equipped with supply chutes whose interior volumes correspond at least to the catalyst volume which prevails or exists when the volume is reduced and in which catalyst material is stored for sliding into the tube area proper when the catalyst volume is reduced. During reactor operation, the tubes are traversed lengthwise by a mixture of materials to be reacted which enters at the upper ends of the tubes and escapes at the lower ends of the tubes.
An object of the present invention is to provide a reformation reactor in which, at relatively low expense, measures are provided to reduce reduction of the volume of catalyst material in the reaction chamber and a resultant undesired reduction of the reaction rate during the operation of the reactor.
The foregoing object has been achieved in accordance with the present invention by providing a reformation reactor in which a catalyst supply container is associated with the reaction chamber. The container is connected with the chamber so that catalyst material is automatically added from the supply container to the reaction chamber. In this way, automatic loading of catalyst material into the reaction chamber is provided, thus compensating for a possible reduction in the volume of the catalyst charge in the reaction chamber. Such a reduction of volume occurs for example in highly loaded methanol reformation catalysts. A high load of catalyst material is required in particular when operating a methanol reformation reactor to generate hydrogen for a fuel cell system in mobile applications for structural reasons.
In the reformation reactor according to the present invention, the catalyst material emerging from the supply container enters the reaction chamber at a point subjected to the flow of gas which has already been reacted partially in the reaction chamber. This measure is especially advantageous for hydrogen reformation of methanol. In this situation, the partially reacted gas already contains a small amount of hydrogen. This hydrogen can be used to form a previously unformed catalyst material, for example for reducing a metal oxide as unformed material into the free metal as the formed catalyst material. Consequently, the catalyst material can be supplied to the supply container in its unformed state which is usually much easier to handle.
In a further improvement on the integrated forming device of the present invention, a gas-permeable heat-conducting reaction guide plate is located at the inlet so that the catalyst material enters from the supply container on the side of the plate facing away from the gas stream into the reaction chamber. With the plate, therefore, the quantity of gas which impacts the catalyst material entering the reaction chamber can be controlled as needed. This control is especially important when unformed catalyst material is stored and can then be formed in a controllable reaction on the side of the reaction guide plate located at the rear in the gas flow direction, for example with the already formed hydrogen quantity from the reformation reaction. The heat which is produced in this exothermal reaction can be carried away by the heat-conducting reaction guide plate to avoid overheating. The heat which is carried away can be supplied to the catalyst material located on the opposite side of the plate, already formed, and catalyzing the endothermal methanol reformation reaction.
The reformation reactor according to the present invention incorporates a device located in the supply container for exerting a position-determining pressure on the catalyst material. Because the supply container is connected to the reaction chamber, the catalyst charge is also positionally fixed in the reaction chamber in a generally simultaneous manner. This position establishment minimizes abrasion phenomena in the catalyst charge which would otherwise occur especially in mobile applications because of the vibration acting on the reactor.
In a yet further improvement of the reformation reactor according to the present invention, the supply container has a vent device so that gases which enter, for example, because of a catalyst formation reaction at the connecting location between the supply container and the reaction chamber into the supply container, can be vented to the exterior.
In a further embodiment of the reformation reactor according to the present invention, the catalyst material is stored in the supply container in the unformed state. Because the unformed material is usually less reactive than the catalyst material in the formed state, the handling of the material is facilitated before and during its addition to the supply container. No special measures are required to keep the catalyst material in the supply container even when stored for long period of time in the formed state.